Extending storage time of removed plasma chamber components prior to cleaning thereof

ABSTRACT

A method of extending storage time prior to cleaning a component of a plasma chamber is provided. The method comprises removing the component from the chamber, covering a thermal spray coating on the component while the surface is exposed to atmospheric air, storing the component, optionally removing the covering, and optionally wet cleaning reaction by-products from the thermal spray coating. Alternatively, instead of, or in addition to covering a thermal spray coating on the component, the component can be placed into a desiccator or dry-box.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 11/239,396 entitled EXTENDING STORAGE TIME OF REMOVED PLASMA CHAMBERCOMPONENTS PRIOR TO CLEANING THEREOF, filed on Sep. 30, 2005 now U.S.Pat. No. 7,976,641, the entire content of which is hereby incorporatedby reference.

BACKGROUND

As semiconductor technology evolves, decreasing transistor sizes callfor an ever higher degree of accuracy, repeatability and cleanliness inwafer processes and process equipment. Fierce competition within thesemiconductor industry calls for ever lower cost per processed wafer.All of these requirements apply generally to all of the processingequipment used in the fabrication sequence.

Among the various types of equipment that exists for semiconductorprocessing is equipment that involves the use of plasmas, such as plasmaetch, plasma-enhanced chemical vapor deposition (PECVD) and resist stripequipment. The types of equipment required for these processes includecomponents which are located within the plasma chamber, and mustfunction in that environment. The environment inside the plasma chambermay include exposure to the plasma and to etchant gasses, and materialsused for such components are preferably adapted to withstand theenvironmental conditions in the chamber.

Generally, replacement of such components is expensive, and componentlifetime as measured by the total number of wafers processed beforereplacement is needed is typically the denominator in the costdetermination. Components with lifetimes that are considered low aretherefore considered expensive and alternative solutions are generallysought. Conversely, methods which extend the lifetime of component partsare considered to lower their cost.

SUMMARY

A method of extending storage time of a removed component of a plasmachamber prior to cleaning thereof comprises removing the component fromthe chamber, covering a thermal spray coating on the component while thesurface is exposed to atmospheric air, and storing the component. Thecovering allows extended storage of the component until a cleaningprocess is performed by removing the covering and cleaning reactionby-products from the thermal spayed coating.

In an embodiment, the covering can be a moisture impermeable materialsuch as a polymer layer sealed to the surface of the component. Inanother embodiment, the component can be placed into a desiccator ordry-box and stored therein until a cleaning process such as wet cleaningis carried out.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic of a conductor etch plasma processing chamberincluding an yttria coated ceramic window.

FIG. 2 depicts an enlarged view of a removed ceramic window positionedwith the side normally facing the chamber upward.

FIG. 3 shows electroplating tape and its preparation for use on theceramic window according to a preferred embodiment

FIG. 4 shows the final configuration of the electroplating tape coveringboth the gas injector and the yttria coated side of the ceramic window.

DETAILED DESCRIPTION

Components used in semiconductor plasma processing chambers can be madefrom such materials as ceramic and anodized aluminum. Such componentssustain physical and chemical attack from the plasma during normalprocessing conditions. In response to this requirement, components canbe coated with an applied outer layer which provides protection from thekinds of chemicals, gasses and by-products of the plasma environment.One type of outer layer that can be applied is a thermal sprayedcoating, e.g. a plasma sprayed coating which contains yttrium oxide, oryttria. An yttria-containing (“yttria”) coating can provide low porositylevels, which serves to insulate the underlying substrate material fromthe aggressive environment of the plasma atmosphere. Other types ofouter layers that can be applied include aluminum oxide, or alumina,cerium oxide or ceria, and the like.

One technique for depositing an yttria or alumina coating is thermalspraying, in which ceramic powder is melted and incorporated in a gasstream directed at the component being spray coated. One version ofthermal spraying is plasma spraying, in which the coating material,usually in powder form, is injected into a high temperature plasmaflame. The powder is heated rapidly, and when it comes in contact withthe target substrate, cools rapidly to form the coating. Thermal sprayyttria coatings can be formed directly on the substrate without havingpreviously treated the substrate to promote adhesion. For example,yttria coatings can be applied directly to ceramic or metal components,e.g. quartz, alumina, anodized aluminum and the like.

An exemplary plasma reactor that can include components with thermalspray coatings such as yttria coatings is the Versys 2300™ etcheravailable from Lam Research Corporation of Fremont, Calif. Asschematically shown in FIG. 1, the reactor comprises a reactor chamber100 that includes a substrate support 101 including an electrostaticchuck 102, which provides a clamping force to a substrate such as asemiconductor wafer (not shown) mounted thereon. The substrate support101 is typically made of anodized aluminum and can also be used to applyan RF bias to the substrate. The substrate can also be back-cooled usinga heat transfer gas such as helium. In the Versys 2300™ etcher,processing gases are introduced into the chamber 100 via a gas injector104 located on the top of chamber 100 and connected to a gas feed 105.The gas injector 104 is typically made of quartz or a ceramic materialsuch as alumina. As shown, an inductive coil 106 can be powered by asuitable RF source (not shown) to provide a high density plasma. Theinductive coil 106 couples RF energy through dielectric window 107 intothe interior of chamber 100. The window 107 is typically made of adielectric material such as quartz or alumina. The window 107 is shownmounted on an annular member 108, typically made of anodized aluminum.The annular member 108 spaces window 107 from the top of chamber 100. Achamber liner 109, typically made of anodized aluminum surrounds thesubstrate support 101. The chamber 100 can also include suitable vacuumpumping apparatus (not shown) for maintaining the interior of thechamber at a desired pressure.

In FIG. 1, selected internal surfaces of reactor components, such as theannular member 108, dielectric window 107, substrate support 101,chamber liner 109, gas injector 104 and the electrostatic chuck 102, areshown coated with a thermal sprayed coating such as an yttria coating110. As shown in FIG. 1, selected interior surfaces of the chamber 100and substrate support 101 below the chamber liner 109 can also beprovided with a thermal sprayed coating such as an yttria coating 110.Any or all of these surfaces, as well as any other internal reactorsurface, can be provided with a thermal sprayed coating such an yttriacoating.

However, while a thermal sprayed yttria coating has low porosity,usually about 5%, and can protect the underlying material of thecomponent from the effects of the plasma, the coating can lacksufficient integrity to prevent penetration of certain reactants. Thisis because a common feature of all thermal spray coatings is theirlenticular or lamellar grain structure resulting from the rapidsolidification of small globules, flattened from striking a cold surfaceat high velocities. While this creates a substantially strong coveringin which mechanical interlocking and diffusion bonding occur, it canalso create micro-fractures within the yttria coating. A poor yttriacoating, for example, may have an open volume of 15%. This means that itcan potentially allow chemicals to penetrate to the anodized aluminumsubstrate.

During plasma etch processes, etchant gasses are used as part of theplasma atmosphere. Some of the different plasma atmospheres for etchapplications include chlorine-containing gasses, oxygen-containinggasses, and fluorine-containing gasses. Often, the chlorine-containinggasses are used in the aluminum etch process, fluorine-containing gassesare used in the silicon, silicon nitride and silicon dioxide etchprocesses, and oxygen-containing gasses are used in the polymeric etchor ash processes. In one kind of aluminum etch process, a structure mayhave photoresist, Ti or TiO₂, Al with 0.5% Cu SiON, Si₃N₄ and SiO₂. Asthe structure is processed in a plasma processing system, chlorine mayreact with aluminum to form aluminum chloride (AlCl₃), an inorganicby-product. This, in turn, can become suspended with organic material,AlF₃, B₂O₃, SiO₂, TiF₄, or photoresist in deposits that adhere tosurfaces within the plasma processing system chamber. Such by-productsare preferably periodically cleaned. For example, etch byproducts can beremoved by contacting the component via wet cleaning using solutions ofsolvents and/or acids such as organic acids. Liquids having a suitablyhigh solubility for metals can be used to remove such metals from thecomponent by the cleaning. Such metals may include Al, B, Ca, Cr, Cu,Fe, Li, Mg, Ni, K, Na, Ti and/or Zn. Suitable solvents that can be usedfor cleaning components to remove etch byproducts include, but are notlimited to, nitric acid (HNO₃), hydrofluoric acid (HF), phosphoric acid(H₃PO₄), oxalic acid (COOH)₂, formic acid (HCOOH), hydrogen peroxide(H₂O₂), hydrochloric acid (HCl), acetic acid (CH₃COOH), citric acid(C₆H₈O₇), and mixtures thereof.

For the purpose of cleaning components as well as to ensure the propercontinuing operation of the system, therefore, part of standardmanufacturing maintenance procedures includes servicing of plasma etchchambers at regular intervals. During such times, the chamber is openedto atmospheric air and components may be removed for cleaning. Interalia, an objective of the cleaning procedure is to remove etchby-products from their surface. This can be done using any known,standard wet cleans designed to remove etch by-products containing bothorganic and inorganic components.

However, it can be the case that a time delay of several days betweenthe removal of the component from the chamber and its subsequent wetclean occurs. This time delay can occur when the resources required tooperate the cleaning station are not available, or for other reasons.During this delay period, typically within 8 hours, peeling of a surfacelayer has been observed. It is herein speculatively suggested that theby-products on the component surface can interact with atmospheric airand produce a chemical reaction. In particular, for components such asthose used in aluminum etch chambers or components having anodizedlayers, by-products can react with moisture in atmospheric air to forman acid. AlCl₃, for example, can react with H₂O to form hydrochloricacid, HCl. A possible reaction is:2AlCl₃+3H₂O=2Al(OH)₃+6HCl

Subsequently, some of this ambient moisture, as well as the createdhydrochloric acid, may diffuse through the thermal spray coating. Foranodized aluminum components, the hydrochloric acid may possibly alsodiffuse through micro-cracks in the anodized aluminum layer to thesubstrate, where it may then react with the aluminum to generatehydrogen gas (H₂). A possible reaction is:6HCl+2Al=2AlCl₃+3H₂

Additionally, the created aluminum chloride, may again react withmoisture to form additional hydrochloric acid, starting the processagain. As sufficient hydrogen gas is produced beneath the anodizedaluminum layer, a gas pocket is formed. Eventually, hydrogen gas maycreate sufficient pressure to substantially damage the layers above it.That is, a blister may be formed that eventually causes the anodizedaluminum and yttria layers to flake off or peel. Regardless ofmechanism, peeling of a surface layer has been observed.

According to a preferred embodiment, thermal spray coated components ofa plasma chamber are covered with a removable material such as asubstantially moisture impermeable polymer sheet capable of being sealed(such as electroplating tape) to the component after removal of thecomponent from the chamber, and maintaining such material securely inplace on the components until such time as the components can be cleanedsuch as by wet cleaning in a process in which the reaction by-productsare generally removed.

Still another embodiment is to place thermal spray coated components ofa plasma chamber into a desiccator or a dry-box with an inert gas suchas nitrogen or argon, or dry air blowing through it, and storing thecomponents within the desiccator or dry-box until such time as thecomponents can be cleaned in a process in which the reaction by-productsare generally removed. The desiccator can be any sealed container with adesiccant such as a box, jar or bag.

It is contemplated to cover thermal spray coated components of a plasmachamber with a substance consisting of a substantially moistureimpermeable solution, gel, paste or foam, and maintaining the substancesecurely in place on the components until such time as the componentscan be cleaned in a process in which the reaction by-products aregenerally removed. It is contemplated that such a substance might beapplied as an aerosol.

It is additionally contemplated that a substance used to cover thermalspray coated components of a plasma chamber may consist of asubstantially moisture absorbing solution, gel, paste, fabric or foam.

The following detailed examples describe processes to extend the storagetime of an yttria coated ceramic window upon removal from a plasmaprocessing chamber after use according to preferred embodiments. Theyare intended to be illustrative rather than exclusionary, since numerousmodifications and variations will be apparent to those skilled in theart.

Example 1

A schematic illustration of a Versys 2300™ conductor etch plasma chamberas shown in FIG. 1 is available from Lam Research Corporation inFremont, Calif. FIG. 2 shows the yttria coated ceramic window 107coating-side up. The yttria coating 110 does not cover an outerring-shaped area referred to as the ceramic sealing surface 201. FIG. 3shows electroplating tape 300, such as 2 mil Green Polyester Tape, part# VGT 215 available from Advanced Paper Systems of San Jose, Calif.,which consists of a substantially moisture impermeable material 302, anadhesive layer 303, and an adhesive cover layer 304.

Procedurally, the tape 300 is prepared by cutting, such that it issubstantially the same dimension as the ceramic window 107. It isfurther prepared such that a ring-shaped adhesive portion 305 which isto be positioned over the ceramic sealing surface 201 is exposed byremoving the adhesive cover in that region. A remaining disk-shapedadhesive portion which is to be positioned over the yttria coatingremains covered by the adhesive cover 306. A schematic of the preparedtape 301 in cross section is shown in FIG. 3 b. The prepared tape 301should be prepared before the chamber is opened.

Immediately after opening the chamber 100 and removing the ceramicwindow 107, while it is still hot as a result of prior plasma etchoperation of the reactor, additional electroplating tape 401 is used toseal the gas injector 104 from the ceramic side, shown in FIG. 4. Thetape 401 is positioned such that substantially all of the trapped airbelow the tape is removed. Also shown in FIG. 4, the prepared tape 301is then applied to the ceramic window such that any trapped air at thesealing surface between the ceramic and the electroplating tape isremoved. The ring-shaped region of the exposed adhesive 305 is thenforced into intimate contact with the ring-shaped ceramic sealingsurface 201. In this way, a substantially airtight seal is achieved atthe periphery of the yttria coated ceramic window, preventing exposureof the surface of the yttria to atmospheric air.

Both the prepared and the additional electroplating tape are preferablyapplied shortly after removing the ceramic window from the chamber. Itis recommended that the application of the prepared and the additionalelectroplating tape is accomplished within five minutes of removing theceramic window from the chamber, or while the ceramic window is stillabove 50° C. Speculatively, moisture absorption from the atmospheric airtakes place substantially after the component has cooled. Regardless ofmechanism, the electroplating tape-sealed yttria-coated ceramic windowis then placed into double packaging bags in preparation for cleaning.

Example 2

Similar to example 1, the tape 300 is sized by cutting such that it issubstantially the same dimension as the ceramic window 107. The tape 300should be sized before the chamber is opened.

Immediately after opening the chamber 100 and removing the ceramicwindow 107, while it is still hot as a result of, prior plasma etchoperation of the reactor, additional electroplating tape 401 is used toseal the gas injector 104 from the ceramic side, shown in FIG. 4. Thetape 401 is positioned such that substantially all of the trapped airbelow the tape is removed.

With the window 107 positioned such that the yttria coating 110 isfacing upwards, cleanroom wipes are used to cover the coating 110without covering the ceramic sealing surface 201. An example ofcleanroom wipes that can be used for this purpose are CleanroomPolyester/Cellulose Blend Wipers, Spec-Wipe™ 3 available from VWRInternational, Inc., West Chester, Pa. Alternatively, a plastic sheetcould be used. The annular section of adhesive cover 304 is thencompletely removed from tape 300 and the central portion of the tape 300without cover is applied to the ceramic window such that any trapped airat the sealing surface between the ceramic and the electroplating tapeis removed. The annular section of exposed adhesive is then forced intointimate contact with the ring-shaped ceramic sealing surface 201 aswell as the wipes covering the yttria coating 110. In this way, asubstantially airtight seal is achieved at the periphery of the yttriacoated ceramic window, preventing exposure of the surface of the yttriato atmospheric air. Further, the exposed adhesive is prevented fromcoming into contact with the yttria coating so as to minimize damagingthe coating.

The present invention has been described with reference to preferredembodiments. However, it will be readily apparent to those skilled inthe art that it is possible to embody the invention in specific formsother than as described above without departing from the spirit of theinvention. The preferred embodiment is illustrative and should not beconsidered restrictive in any way. The scope of the invention is givenby the appended claims, rather than the preceding description, and allvariations and equivalents which fall within the range of the claims areintended to be embraced therein.

1. A method of plasma processing in a plasma processing apparatuscomprising a chamber containing a component having a thermal spraycoating, the method comprising: removing the component, which hasundergone a plasma operation during which reaction by-products weredeposited on a surface of the thermal spray coating of the componentfrom the chamber; covering the surface of the thermal spray coating onthe component while the component is at a temperature of at least 50°C.; storing the component for later cleaning; removing the covering; andperforming a wet cleaning process in which the reaction by-products areremoved from the surface of the thermal spray coating.
 2. A method ofextending storage time prior to cleaning a component of a plasmachamber, the component comprising a thermal spray coating, the methodcomprising: removing the component from the chamber, wherein thecomponent has undergone a plasma operation during which reactionby-products were deposited on the thermal spray coating; placing thecomponent into a desiccator or dry-box at a temperature of at least 50°C.; and storing the component in the desiccator or dry-box.
 3. Themethod of claim 2, wherein placing the component into a desiccator ordry-box is accomplished within 5 minutes of removing the component fromthe chamber, and wherein removing the component from the chamber exposesthe thermal spray coating of the component to atmospheric air.
 4. Themethod of claim 2, wherein the component is at a temperature of at least50° C. when it is removed from the chamber.
 5. The method of claim 2,further comprising: removing the component from the desiccator ordry-box; and wet cleaning the reaction by-products from the thermalspray coating.
 6. The method of claim 2, wherein the thermal spraycoating consists essentially of yttria.
 7. The method of claim 2,wherein the thermal spray coating consists essentially of alumina. 8.The method of claim 2, wherein the thermal spray coating is on anunderlying material selected from the group consisting of aluminum,anodized aluminum, alumina and a ceramic.
 9. The method of claim 2,wherein the plasma chamber is a plasma etch chamber.
 10. The method ofclaim 2, wherein the component is cleaned and reinstalled in thechamber.
 11. The method of claim 2, further comprising: wherein removingthe component from the chamber is from a first plasma chamber, afterstoring the component in the desiccator or dry-box, removing thecomponent from the desiccator or dry-box and performing a cleaningprocess in which reaction by-products are removed from the thermal spraycoating, and reinstalled reinstalling the component in a second plasmachamber.
 12. The method of claim 2, wherein the component comprises adielectric window.
 13. The method of claim 2, wherein the componentcomprises a baffle.
 14. The method of claim 2, wherein the component isselected from the group consisting of: electrostatic chucks, disks,rings, liners, injectors, substrate supports, and gas distributionplates.
 15. The method of claim 1, further comprising after covering thesurface of the thermal spray coating on the component, placing thecomponent into a desiccator or dry-box.
 16. The method of claim 1,wherein the covering is applied outwardly of a periphery of the surfaceof the thermal spray coating.
 17. The method of claim 1, furthercomprising: wherein the chamber is a first plasma chamber, and afterperforming the wet cleaning process in which reaction by-products areremoved from the surface of the thermal spray coating, reinstalling thecomponent in a second plasma chamber.
 18. The method of claim 2, furthercomprising covering a surface of the thermal spray coating on thecomponent prior to placing the component into a desiccator or dry-box.19. The method of claim 18, wherein the covering is applied outwardly ofa periphery of the surface of the thermal spray coating.
 20. A method ofplasma processing in a plasma processing apparatus comprising a chambercontaining a component having a thermal spray coating, the methodcomprising: removing the component, which has undergone a plasmaoperation during which reaction by-products were deposited on a surfaceof the thermal spray coating of the component from the chamber; coveringthe surface of the thermal spray coating on the component while thecomponent is at a temperature of at least 50° C.; and storing thecomponent for later cleaning.